Field of the Invention
The present invention relates to a damper for a drive shaft of a vehicle. More particularly, the present invention relates to an integrated variable frequency damper which may easily tune a damping frequency, and thus may be applied to all types of drive shafts regardless of the type of vehicle, specifications of power trains (PT), and regions.
Description of Related Art
A drive shaft of a vehicle serves to transmit power, which is generated by an engine and transmitted through a transmission, to wheels.
Torsion and bending vibration occur in the drive shaft due to rotational force of the engine, and vibration occurs when a rotational speed of the drive shaft reaches a certain rotational speed while the drive shaft rotates at a high speed.
Vibration, which occurs in the drive shaft, degrades driving stability of the drive shaft, has an adverse effect on a drive system, and generates booming noise that causes deterioration in silence property.
In particular, in a case in which a frequency of the vibration generated in the drive shaft is matched with a natural frequency of the drive shaft, booming noise is increased as the frequency is further increased, and the increased vibration causes resonance, which may destroy the drive shaft or may cause fatal damage to the drive shaft.
A horizontal length of the drive shaft is changed depending on a size of the vehicle and positions at which the engine and the transmission are mounted, and as a diameter and a shape of the drive shaft are changed, a resonant frequency is also changed.
In general, the resonant frequency of the drive shaft is matched with a portion vulnerable to acceleration noise and vibration of the vehicle, which is the main cause of deterioration in NVH (noise, vibration, and harshness) performance of the vehicle.
Therefore, as illustrated in FIG. 1, a dynamic damper 110, which is adapted to a resonant frequency of the drive shaft, is installed on a drive shaft 1 in order to reduce vibration and noise.
The damper 110 generates vibration with a certain frequency, which may cancel vibration generated in the drive shaft 1, and cancels the vibration, thereby ensuring stability of the drive shaft and the drive system, and minimizing the occurrence of noise.
FIG. 2 is a configuration view illustrating a cross-sectional shape of the dynamic damper according to the related art, and the dynamic damper 110 includes a mass body 120 which is made of a metallic material and defines mass, a hollow damper body 130 which is made of an elastic rubber material and formed to surround the mass body 120, and banding members 140 which fix the damper body 130 to the drive shaft 1.
The dynamic damper 110 is mounted on an outer circumferential surface of the drive shaft 1. The damper body 130 to which the mass body 120 is coupled is fitted with the outer circumferential surface of the drive shaft 1, the banding members 140 are fastened to both end portions of the damper body 130, and then the banding members 140 are tightened, so that the dynamic damper 110 is fixed to the drive shaft 1.
Therefore, both the end portions of the damper body 130 are coupling portions 131 that are fixed to and supported on the drive shaft 1 by the banding members 140, and bridge portions 132, which are connected between a portion where the mass body 120 is installed and the coupling portions 131, are rigid portions that exhibit rigidity.
A natural frequency of the dynamic damper 110 is changed depending on rigidity k that depends on mass of the mass body 120 and physical properties of the rubber material that constitutes the damper body 130 including the rigid portion 132.
FIG. 3 is a view illustrating a one-degree-of-freedom model of the drive shaft and the dynamic damper. The damper is being developed to be adapted to the resonant frequency of the drive shaft, and a control frequency of the dynamic damper may be tuned in accordance with changes in mass and rigidity of the drive shaft.
However, significant development costs, such as costs required to manufacture molds, are required to manufacture the dynamic damper that is adapted to the resonant frequency of the drive shaft, and as a result, there is a need for an integrated damper system that may be easily tuned and applied to various types of vehicles and drive shafts.
Typically, a damping frequency is implemented by tuning values of mass and and rigidity kd of the damper (mass body), and the damping frequency of the damper is changed depending on the type of vehicle and a difference in power trains (PT) such as the engine, the transmission, and the like.
The main frequency of the damper is also changed depending on a regional and seasonal variation in temperature, and as a result, there is inconvenience because various types of dampers need to be developed and manufactured to satisfy the above conditions, and significant costs are required to develop and manufacture various types of dampers.
The prior art discloses a variable dynamic damper for a propeller shaft, in which a fluidic material with high specific gravity, which allows weight transition of a weight by means of centrifugal force that is changed depending on a rotational speed, is injected into the propeller shaft, thereby effectively reducing noise and vibration within a certain frequency region that is changed depending on a rotational speed of the propeller shaft while the vehicle travels.
As described above, a technology, which controls frequency properties that are changed depending on a rotational speed, is known as a technology in the related art, but a damper system, which may easily tune a frequency to a desired frequency, is not proposed.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.